Method for producing monocyclic ketones c4-c5

ABSTRACT

The invention relates to a method for producing monocyclic ketones C 4 -C 5 . The inventive method is based on the reaction of a liquid-phase oxidation of monocyclic alkenes C 4 -C 5  into corresponding cyclic ketones by nitrogen oxide or the mixture thereof with an inert gas. The process is carried out at a temperature ranging from 20 to 300° C. and a pressure of nitrogen oxide ranging from 0.01 to 100 atm. The inventive process ensures the high selectivity with respect to target products, the explosion safety at work and is promising for industrial use.

FIELD OF THE INVENTION

The present invention relates to a method for producing monocyclicketones C₄-C₅ and more particularly to a method for producing thereof byliquid-phase oxidation of corresponding liquid alkenes using nitrousoxide (N₂O).

Cyclic ketones are valuable intermediate products in the synthesis ofvarious organic compounds. For instance, cyclopentanone is used forsynthesizing δ-valerolactone, ghlutaric acid, as well as sebacic acid,which is used for producing Nylon-6,10. Cyclopentanone is also used as asolvent.

BACKGROUND OF THE INVENTION

There are known several methods for producing lower cyclic ketones. Forexample, according to U.S. Pat. No. 2,223,494, C07C 29/50, 1940,cyclopentanone and cyclobutanone are produced by the oxidation ofcyclopentane and cyclobutane, respectively, with air oxygen. Thereaction is carried out at 120-170° C., using Co, Mn, Cu, Ce salts as acatalyst. This method is disadvantageous in that a large amount ofcyclic alcohol is formed along with the ketone, and in that selectivitydrops sharply as the conversion increases.

Cyclopentanone can also be produced by catalytic dehydrogenation ofcyclopentanol in the gaseous phase at 250-375° C. over a Cu—Zn catalyst[U.S. Pat. No. 2,377,412, C07C 45/00, 1945] or at 160-250° C. over a Nicatalyst [U.S. Pat. No. 2,371,794, C07C 5/05, 1945]. Practicalapplication of this method involves difficulties in view of the absenceof cheap sources of cyclopentanol.

A method is known for producing cyclopentanone from adipic acid [U.S.Pat. No. 5,856,581, C07C 45/48, 1999] or esters thereof [U.S. Pat. No.4,745,228, C07C 45/48, 1988] in the presence of oxide catalysts. Apartfrom high cost of the feed stock, the first method is disadvantageous inthe necessity of carrying out the process in an aggressive acid mediumat a high temperature (200-300° C.). In the case of using esters, anadditional step of preparing the latter is required, the processflowsheet becoming thus complicated.

According to U.S. Pat. No. 4,806,692, C07C 45/34, 1989, cyclopentanonescan also be produced by the oxidation of cyclopentene in the liquidphase with air oxygen, using a homogeneous catalyst PdCl₂-CuCl₂ at atemperature of up to 80° C. This method is disadvantageous in a lowefficiency of the process and the necessity of using aggressive HClsolution.

In GB Pat. No. 649680, C07C 45/34, 1951 there is claimed a process forthe oxidation of olefins into carbonyl compounds with nitrous oxide.According to this process, in particular, it is possible to producecyclopentanone by oxidizing cyclopentene. This process isdisadvantageous in a low efficiency and severe reaction conditions.

A second serious disadvantage of this process is the possibility offlammable mixtures to be formed. In order to rule out explosion hazards,the authors of said GB Patent propose to introduce additionallysaturated hydrocarbons into the reaction mixture.

However, as later investigations have shown, mixtures of saturatedhydrocarbons with N₂O are almost as explosion-hazardous, as mixtures ofolefins. Thus, limit concentrations of propylene in N₂O are 1.8 to26.8%, and limit concentrations of propane are 2.1 to 24.8% [G.Panetier, A. Sicard, V Symposium on Combustion, 620 (1995); B. B.Brandt, L. A. Matov, A. I. Rozlovsky, V. S. Khailov, Khim. Prom., 1960,No. 5, pp. 67-73 (in Russian)]. Therefore saturated hydrocarbons, inspite of their smaller reactivity, cannot serve as a means for rulingout explosion hazards.

SUMMARY OF THE INVENTION

The present invention protects a method for producing cyclobutanone andcyclopentanone by oxidizing cyclic alkenes C₄H₆ and C₅H₈, this methodbeing free of the above-indicated disadvantages. For example, in thecase of cyclopentene the reaction proceeds according to the followingequation:

According to this method, for enhancing selectivity, the reaction iscarried out under milder conditions, when cycloalkenes are present inthe form of a liquid phase, wherein the reaction proceeds with a highselectivity. Excessive increase of the N₂O temperature and/or pressureis undesirable, because it may lead to lowering the selectivity owing tocontribution made by the gas phase oxidation.

Explosion-safe operation conditions according to the proposed method areprovided by adding an inert gas which does not react with N₂O, forinstance, nitrogen, argon, helium, carbon dioxide gas, etc., or amixture thereof, to the reaction mixture. Effluent gases of the reactioncan play the role of an inert gas. In different steps of the process,depending on the “cycloalkene:nitrous oxide” ratio, the proportion of aninert gas, required for ensuring explosion-safe operation, can bedifferent and be provided by supplying such gas separately. From thestandpoint of simplicity and maximum safety of the process, it isexpedient to have such dilution of nitrous oxide with an inert gas thatthe reaction mixture should be not explosion-hazardous at any content ofcycloalkene. This condition is fulfilled, if the content of N₂O in themixture with an inert gas is not greater than 25%. The use of such amixture rules out the origination of explosion-hazardous situations inall the steps of the process.

For decreasing explosion-hazardousness, burning inhibitors, such astrifluorobromomethane, difluorochlorobromomethane,dibromotetrafluoroethane and others, can be added to the reactionmixture.

In accordance with the present invention, the oxidation of monocyclicalkenes C₄-C₅ into cyclic ketones can be carried out within a wide rangeof conditions both in a static and in a flow reactor which can bemanufactured from steel, titanium, glass, or any other suitablematerial. All known techniques increasing the efficiency of gas-liquidreactions can be employed in this case.

In the case of a static variant, cycloalkene is introduced into a nautoclave (without a solvent or with a solvent) in such amount that uponheating to the temperature of the reaction cycloalkene should be presentin the form of liquid phase. Then nitrous oxide or its mixture with aninert gas is supplied, the pressure being brought to a preset value. Theamount of nitrous oxide is selected such that its pressure at thereaction temperature should be 0.01 to 100 atm. After that the reactoris heated to the reaction temperature within a range of 20 to 300° C.The reaction time is selected depending on the conditions under whichthe reaction is carried out, as well as on the requirements to be met bythe process, and may vary from several minutes to several tens of hours.

The reaction of oxidation of cycloalkenes C₄-C₅ can be carried outeither without a solvent or with a solvent which can be selected from awide range of substances conventionally employed in the practice oforganic synthesis. The reaction proceeds with a sufficiently high ratewithout a catalyst. However, it can be conducted also with the use of acatalyst.

The proposed method for producing cyclic ketones does not require highpurity of the starting reagents. Thus, nitrous oxide can be used both inpure form and in admixtures of various gases which do not affectadversely the reaction characteristics. Cycloalkenes C₄-C₅ may alsocontain admixtures of various organic compounds, especially if they donot contain double bonds C═C.

The essence of the proposed invention is illustrated by the followingExamples.

EXAMPLES 1-5

These Examples (Table 1) demonstrate high selectivity of theliquid-phase oxidation reaction with the help of nitrous oxide.

Example 1. 33 cm³ of cyclopentene (Aldrich, 99%) are poured into a 100cm³ reactor made from stainless steel and provided with a stirrer (ParrCo.). The reactor is purged with nitrous oxide, and then the pressure ofnitrous oxide is brought to 10 atm. The reactor is heated to 197° C. andmaintained at this temperature during 5 hrs. On completion of thereaction, the reactor is cooled down to room temperature, the pressureis measured, and the final composition of the gaseous and liquid phasesis analyzed by gas chromatography and chromatography-mass spectrometrytechniques. From the obtained data the conversion of cyclopentene andthe selectivity of the reaction for cyclopentanone are calculated;$\begin{matrix}{X = {{\frac{C_{CyON} + {\sum C_{side}}}{C_{CyEN}^{0}} \cdot 100}(\%)}} & (2) \\{{S = {{\frac{C_{CyON}}{C_{CyON} + {\sum C_{side}}} \cdot 100}(\%)}},} & (3)\end{matrix}$where C_(CyEN) ⁰ is the initial cyclopentene concentration; C_(CyON) isthe cyclopentene concentration in reaction products; ΣC_(side) is thetotal concentration of by-products. In the case of large conversions,the value X can be calculated also from the difference between theinitial and final concentrations of cyclopentene: $\begin{matrix}{X = {{\frac{C_{CyEN}^{0} - C_{CyEN}}{C_{CyEN}^{0}} \cdot 100}(\%)}} & (4)\end{matrix}$

Example 2 is similar to Example 1, the difference being in that thereaction is carried out at 195° C. during 12 hours.

Example 3 is similar to Example 2, the difference being in that thereaction is carried out at a temperature of 150° C.

Example 4 is similar to Example 3, the difference being in that thereaction is carried out at 175° C. during 10 hours.

Example 5 is similar to Example 4, the difference being in that thereaction is carried out at 225° C. during 3 hours. TABLE 1 Example T (°C.) Time (hrs) X (%) S (%) 1 197 5 7.7 98 2 195 12 15.6 97 3 150 12 3.597.5 4 175 10 8.5 98 5 225 3 13 99

EXAMPLE 6

This Example is a comparative one. The experiment is carried out as inExample 1, the difference being in that the reactor is charged with 5 mlof cyclopentene. With such charging under the reaction conditions thewhole of the cyclopentene is in the gaseous phase. As a result of theexperiment, the conversion of cyclopentene was approximately 0.5%. Thisresult indicates that under the abovesaid conditions the reaction in thegas phase practically does not go.

EXAMPLES 7-8

These Examples, as compared with Example 1, demonstrate the influence ofthe nitrous oxide concentration on the process characteristics (Table2). The nitrous oxide concentration in the reaction mixture is preset bythe value of its initial pressure at room temperature, P_(N) ₂ _(O) ⁰.

Example 7 is similar to Example 1, the difference being in that theinitial pressure of nitrous oxide at room temperature in this experimentis set to be equal to 25 atm.

Example 8 is similar to Example 1, the difference being in that theinitial pressure of nitrous oxide in this experiment is set to be equalto 5 atm. TABLE 2 Example P_(N) ₂ _(O) ⁰ (atm) T ° C.) X (%) S (%) 1 10197 7.7 98 7 25 197 20.5 99 8 5 197 4.0 98

EXAMPLES 9-10

Examples 9-10 (Table 3) demonstrate the possibility of carrying out theprocess in the presence of a catalyst.

Example 9 is similar to Example 1, the difference being in that thereaction is carried out in the presence of 0.15 g of Fe₂O₃/SiO₂ (2.8 wt.% of Fe₂O₃). The catalyst is prepared by impregnating SiO₂ with asolution of FeCl₃, dried at 110° C. and calcined in air at 500° C. for 2hrs.

Example 10 is similar to Example 1, the difference being in that thereaction is carried out in the presence of 0.5 g of Ag/SiO₂ (1 wt. % ofAg). The catalyst is prepared by impregnating SiO₂ with a solution ofAgNO₃, dried at 110° C. and calcined in air at 500° C. for 2 hrs. TABLE3 Example Catalyst T (° C.) X (%) S (%) 9 Fe₂O₃/SiO₂ 197 7.5 97.5 10Ag/SiO₂ 197 8 97

EXAMPLES 11-14

These Examples demonstrate the possibility of cyclopentene oxidation inthe presence of a solvent (Table 4).

Example 11 is similar to Example 1, the difference being in that 10 mlof cyclopentene and 75 ml of isobutanol are poured into the reactor.

Example 12 is similar to Example 1, the difference being in that 10 mlof cyclopentene and 50 ml of cyclohexane are poured into the reactor.

Example 13 is similar to Example 3, the difference being in that 10 mlof cyclopentene and 50 ml of acetonitrile are poured into the reactor.

Example 14 is similar to Example 13, the difference being in thatinstead of acetonitrile use is made of heptane and the reaction iscarried out at 220° C. for 5 hrs. TABLE 4 Example Solvent T (° C.) X (%)S (%) 11 Isobutanol 195 15.6 98 12 Cyclohexane 195 12.6 98 13Acetonitrile 150 2.5 97.5 14 Heptane 220 32.2 99.0

EXAMPLES 15-20

Examples 15-20 (Table 5) demonstrate the possibility of carrying out thereaction with diluted mixtures of nitrous oxide.

Example 15 is similar to Example 7, the difference being in that insteadof pure nitrous oxide its mixture with an inert gas—nitrogen is fed tothe reactor, in which mixture the concentration of N₂O is 70% Theinitial pressure of the mixture in the reactor (P⁰) is set to be 49 atm.

Example 16 is similar to Example 15, the difference being in that theconcentration of N₂O in the mixture with nitrogen is 20%.

Example 17 is similar to Example 16, the difference being in that theinitial pressure in the reactor is set to be 98 atm. The reaction iscarried out at 195° C. for 12 hours.

Example 18 is similar to Example 15, the difference being in that theconcentration of nitrous oxide is 50%, and the initial pressure of themixture of N₂O and N₂ is set to be 32 atm. The reaction is carried outat 225° C. for 3 hours.

Example 19 is similar to Example 17, the difference being in thatinstead of nitrogen argon is used, in which the concentration of nitrousoxide is 40%. The initial pressure of the mixture of N₂O and Ar is setto be 43 atm.

Example 20 is similar to Example 19, the difference being in that carbondioxide gas is used instead of argon. TABLE 5 Concen- tration of N₂O inInert P⁰ mixture Time Example gas (atm) (%) T (° C.) (hrs) X (%) S (%)15 N₂₂ 49 70 197 5 22.0 98 16 N₂ 49 20 197 5 4.0 98 17 N₂ 98 20 195 1215.0 97 18 N₂ 32 50 225 3 14.0 99 19 Ar 43 40 195 12 16.2 99 20 CO₂ 4340 195 12 15.8 98

Examples 15-20 demonstrate that cyclopentene is oxidized with a highselectivity into cyclopentanone with the aid of nitrous oxide dilutedwith an inert gas. The content of nitrous oxide in a mixture with aninert gas can be varied in a wide range, including the range of N₂Oconcentrations of 25% and less, in which the possibility of explosionhazardous situations is ruled out in any compositions with cycloalkeneC₄-C₅. As Examples 16-17 demonstrate, the oxidation of cycloalkenes inthis range proceeds with a high efficiency.

In the present invention there is proposed a new method for producingcyclic ketones C₄-C₅, based on the reaction of liquid-phase oxidation ofcyclic alkenes C₄H₅ and C₅H₈ with nitrous oxide or a mixture thereofwith an inert gas. The process provides high selectivity, explosionsafety and is promising for industrial application.

1. A method for producing monocyclic ketones C₄-C₅, carried out bycontacting a liquid cycloalkene with nitrous oxide at a temperature of20 to 300° C. and a pressure of nitrous oxide of 0.01 to 100 atm.
 2. Amethod according to claim 1, wherein a diluent inert gas is introducedinto the reaction mixture.
 3. A method according to claim 1, wherein theconcentration of an inert gas in the reaction mixture does not exceed99%.
 4. A method according to claim 1, wherein the concentration of aninert gas is selected such as to rule out the possibility ofexplosion-hazardous compositions to be formed in each step of theprocess.
 5. A method according to claim 1, wherein the concentration ofan inert gas is selected such as to rule out the possibility ofexplosion-hazardous compositions to be formed in all steps of theprocess.
 6. A method according to claim 1, wherein the reaction iscarried out at a temperature of 20 to 199° C. and a pressure of nitrousoxide of 0.01 to 100 atm.
 7. A method according to claim 1, wherein thereaction is carried out at a temperature of 20 to 300° C. and a pressureof nitrous oxide of 0.01 to 20 atm.
 8. A method according to claim 1,wherein the reaction is carried out in the presence of a catalyst.
 9. Amethod according to claim 1, wherein the reaction is carried out in thepresence of a solvent.
 10. A method according to claim 1, whereinnitrous oxide contains admixtures of other gases which do not impair theprocess characteristics.
 11. A method according to claim 1, wherein thereaction is carried out in a static or flow reactor.
 12. A methodaccording to claim 1, wherein recirculating gases are used for carryingout the reaction.